Digital disks such as compact disks (CDs) or digital versatile disks (DVDs) may include a multiple layer process for manufacture. The disk may include a substrate having a pattern of microscopic pits or readout information applied thereto. The pattern of pits includes the digital readout information for the disk. The substrate may have one or more layers applied to it. The readout surface may have a metal applied to the surface using a surface transfer process (STP). The surface transfer process includes producing a single or dual-layer readout surface that includes a sputtered-on reflective (e.g., aluminum) layer on a temporary substrate. The temporary substrate may include polymethylmethacralate (PMMA). The metallized layer portion, which includes the metal and the temporary substrate, is transferred to the already-molded readout layer (with the readout information) having a lacquer layer formed thereon. The PMMA temporary substrate is bonded to the lacquer then, the PMMA temporary substrate is removed from the metallized portion.
Removal of the temporary substrate may be performed by a stripping procedure that typically includes three steps. In the first step, a mechanical device with a knife-edge is inserted between the two half disks at the inside diameter to force separation between the two disks. Next, air pressure is applied in the separation area to propagate the separation. Finally suction cups are employed on the top and bottom surfaces of the disk to pull the halves apart. The temporary substrate is then discarded.
This technique has several significant drawbacks. In the conventional mechanical stripping process, alignment of the knife edge to the inside diameter is critical. The mechanical stripping process described above also creates dust and debris, which may result in reduced product quality. Disks with lacquer or other materials in their moat (edge) area are difficult to separate using the conventional mechanical stripping technique. In addition, the reliability of the temporary substrate removal process often suffers from reliability problems due to surface defects in the metalization layer as a result of the stripping process.